This invention relates to rotary compressors and expansion engines and, more specifically, to compressors and expansion engines of the type which have a rotor supported for planetary movement within a housing and wherein the rotor has a peripheral surface forming a profile of hypotrochoidal configuration and the housing inner surface that is substantially the outer envelope traced by the rotor upon relative rotary motion of the rotor. Such a compressor or expansion engine is disclosed in British Pat. No. 583,035 granted Dec. 5, 1946 to Maillard and the U.S. Pat. No. 4,012,180, dated Mar. 15, 1977, and is generally known as a Maillard-type compressor or engine. The invention will herein be described in terms of a compressor and its operation although, as will be apparent, it also has application to expansion engines.
The efficiency of a rotary compressor depends upon the provision of adequate sealing of each of the working chambers, one from the other. Accordingly, in a Maillard type compressor, it is desirable to provide as effective a sealing as possible between each rotor nose portion and the inner peripheral surface of the housing. Such sealing is particularly difficult in the Maillard type compressor because the line of sealing shifts about the rounded nose portion as the rotor rotates relative to the housing. The use of a seal bar carried in a slot extending across the nose portions of the rotor, as is done in an epitrochoidal rotary mechanism, is not a practical solution to the problem of effectively sealing a Maillard type compressor. Other solutions are exemplified in the aforesaid U.S. Pat. No. 4,012,180 directed to labyrinth seals, the U.S. Pat. to Berkowitz, No. 4,018,548 dated Apr. 19, 1977 directed to an elastic sealing surface on the inner peripheral surface of the housing and the U.S. Pat. No. 4,043,714 dated Aug. 23, 1977 to Berkowitz directed to an expandable and retractable plate type seal covering each nose portion of a rotor. All of these solutions are relatively expensive and unsuitable for relatively inexpensive compressors.
Accordingly, it is an object of this invention to provide a relatively inexpensive and efficient compressor of the Maillard type.
Another object of the present invention is to provide a Maillard type compressor wherein efficiency is attained without sealing devices carried in the nose portions of the rotor.